Dynamic spine stabilizers

ABSTRACT

Treatment of spinal irregularities, including, in one or more embodiments, dynamic spine stabilizers and systems that can be used to stabilize one or more motion segments in a patient&#39;s spine. Spine stabilization systems may comprise a first bone fastener configured to attach the spine stabilization system to a first vertebra. Spine stabilization systems further may comprise a second bone fastener configured to attach the spine stabilization system to a second vertebra. Spine stabilization systems further may comprise a dynamic spine stabilizer configured to connect the first bone fastener and the second bone fastener with at least some relative movement between the first bone fastener and the second bone fastener.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 13/921,545, filed Jun. 19, 2013, which is adivisional application of U.S. patent application Ser. No. 12/635,819,filed Dec. 11, 2009, now issued as U.S. Pat. No. 8,491,638, each ofwhich is incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present disclosure generally relates to treatment of spinalirregularities. In particular, in one or more embodiments, the presentdisclosure relates to dynamic spine stabilizers and systems that can beused to stabilize one or more motion segments in a patient's spine.

BACKGROUND

The spine includes a series of joints routinely called motion segmentunits, which is the smallest component of the spine that exhibitskinematic behavior characteristic of the entire spine. The motionsegment unit is capable of flexion, extension, lateral bending andtranslation. The components of each motion segment unit include twoadjacent vertebrae and their apophyseal joints, the intervertebral disc,and the connecting ligamentous tissue. Each component of the motionsegment unit contributes to the mechanical stability of the joint.

Components of a motion segment that move out of position or becomedamaged can lead to serious pain and may lead to further injury to othercomponents of the spine. Depending upon the severity of the structuralchanges that occur, treatment may include fusion, discectomy, orlaminectomy.

Underlying causes of structural changes in the motion segment unitleading to instability include trauma, degeneration, aging, disease,surgery, and the like. Thus, rigid stabilization of one or more motionsegment units may be an important element of a surgical procedure incertain cases (e.g., injuries, deformities, tumors, etc.), whereas it isa complementary element in others (e.g., fusion performed due todegeneration). The purpose of rigid stabilization is the immobilizationof a motion segment unit Rigid stabilization typically results in arigid, internal fixation of all or part of intervertebral joints andusually involves metallic rods, screws, plates, and the like forstabilization. In general, the devices are intended to immobilize themotion segment.

In addition to a loss of mobility, total immobilization of the motionsegment also can cause unloading of the disk. This can undesirablyimpact fusion, for example, slowing or even reducing the growth of boneinto our through an implant placed into the disc space. Additionally,unloading of the disc can lead to further degeneration of the disk inthe immobilized motion segment. Another drawback is that totalimmobilization also can cause the mobility of the motion segment to betransferred to other motion segments of the spine. The added stressestransferred to motion segments neighboring or nearby the immobilizedsegment can cause or accelerate the degeneration of those segments.

Thus, there is a need for improved systems that can stabilize motionsegments with reduced degeneration of neighboring joints with faster andmore substantial fusion.

SUMMARY

An embodiment of the present invention provides a spine stabilizationsystem. The spine stabilization system may comprise a first bonefastener configured to attach the spine stabilization system to a firstvertebra. The spine stabilization system further may comprise a secondbone fastener configured to attach the spine stabilization system to asecond vertebra. The spine stabilization system further may comprise adynamic spine stabilizer configured to connect the first bone fastenerand the second bone fastener with at least some relative movementbetween the first bone fastener and the second bone fastener.

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention in order that the detaileddescription of the invention that follows may be better understood.Additional features and advantages of the invention will be describedhereinafter that form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand the specific embodiments disclosed may be readily utilized as abasis for modifying or designing other embodiments for carrying out thesame purposes of the present invention. It should also be realized bythose skilled in the art that such equivalent embodiments do not departfrom the spirit and scope of the invention as set forth in the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

These drawings illustrate certain aspects of the present invention andshould not be used to limit or define the invention.

FIG. 1 illustrates a stabilized motion segment in accordance with oneembodiment of the present invention.

FIG. 2 is a perspective view of a dynamic spine stabilizer incorporatinga spring in accordance with one embodiment of the present invention.

FIG. 3 is a perspective view of a dynamic spine stabilizer incorporatinga spring in accordance with another embodiment of the present invention.

FIGS. 4-6 are perspective, end and top views of a dynamic spinestabilizer laterally offset from the bone fasteners in accordance withone embodiment of the present invention.

FIGS. 7-9 are perspective, end and top views of a dynamic spinestabilizer laterally offset from the bone fasteners in accordance withanother embodiment of the present invention.

FIGS. 10-11 are perspective views of a dynamic spine stabilizerlaterally offset from the bone fasteners in accordance with anotherembodiment of the present invention.

FIG. 12 is a perspective view of a dynamic spine stabilizerincorporating one or more spring washers in accordance with oneembodiment of the present invention.

FIG. 13 is a perspective view of a dynamic spine stabilizerincorporating a concave bowed segment in accordance with one embodimentof the present invention.

FIG. 14 is a perspective view of a dynamic spine stabilizerincorporating a convex bowed segment in accordance with one embodimentof the present invention.

FIG. 15 is a perspective view of a dynamic spine stabilizerincorporating one or more compressible elements in accordance with oneembodiment of the present invention.

FIG. 16 is a top view of a cross member for use with the dynamic spinestabilizer of FIG. 15 in accordance with one embodiment of the presentinvention.

FIG. 17 is a perspective view of a bone fastener for use with thedynamic spine stabilizer of FIG. 15 in accordance with one embodiment ofthe present invention.

FIG. 18 is a perspective view of a dynamic spine stabilizerincorporating one or more compressible elements in accordance withanother embodiment of the present invention.

FIG. 19 is a perspective view of a dynamic spine stabilizerincorporating one or more compressible elements in accordance withanother embodiment of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The present invention is generally directed to dynamic spine stabilizersand systems that can be used to stabilize one or more motion segments ina patient's spine. Instead of completely immobilizing the motionsegment, embodiments of the dynamic spine stabilizers allow for at leastsome movement of the motion segment. By way of example, the dynamicspine stabilizers may allow for bending (angular) and/or axial(translational) movement. While embodiments of the dynamic spinestabilizers may be particularly suited for posterior cervicalstabilization, it should be understood that the stabilizers may be usedon the cervical, thoracic, lumbar, and sacral segments of the spine. Inaddition, the stabilizers may be used with the anterior, antero-lateral,lateral, and/or posterior portions of at least one motion segment.

FIG. 1 illustrates a pair of dynamic spine stabilization systems 10implanted in a patient's spine for stabilizing a motion segment 20 inaccordance with one embodiment of the present invention. While only onepair of dynamic spine stabilization systems 10 are illustrated, itshould be understood that more than two dynamic spine stabilizationsystems 10 can be implanted into a patient's spine as desired for aparticular procedure. In addition, while the pair of dynamic spinestabilization systems 10 is illustrated on either side of the motionsegment 20, it should be understood that two or more spine stabilizationsystems 10 may be placed on one side of the patient's spine forstabilization. For example, additional spine stabilization systems 10may be placed along the spine superior or inferior to the motion segment20. Moreover, one or more stabilization systems that incorporate a rigidrod—rather than a dynamic stabilizer—may also be used in conjunctionwith the dynamic spine stabilization systems 20. It should be understoodthat suitable transverse rods may also be incorporated to link thedynamic spine stabilization systems 10 on either side of the motionsegment 20.

As illustrated, each of the dynamic spine stabilization systems 10 mayinclude a dynamic stabilizer 30 coupled to the bone fasteners 40. Thedynamic stabilizer 30 advantageously provides stabilization whileproviding at least some movement of the motion segment 20. By way ofexample, the dynamic stabilizer 30 should provide for relative movementbetween the adjacent vertebrae 50. The bone fasteners 40 generallyshould fix the pair of dynamic spine stabilization systems 10 to theadjacent vertebrae 50. Suitable bone fasteners 40 may include any of avariety of fasteners that may be coupled to the dynamic stabilizer 30while remaining securely fastened to the intended bone. Thus, examplesof suitable bone fasteners 40 include polyaxial screws, helical blades,expandable screws, such as Mollie bolt type fasteners, which areinserted or screwed into the bone and expanded by way of some type ofexpansion mechanism, conventional pedicle screws, staples, hooks, andthe like.

FIG. 2 illustrates dynamic stabilizer 30 in accordance with oneembodiment of the present invention. As illustrated, the dynamicstabilizer 30 comprises a spring 60 disposed between rod portions 70. Inan embodiment, the spring 60 is in the general shape of a V having, forexample, legs 80 with a rectangular cross section. The rod portions 70may be configured and adapted for insertion into rod-receiving membersof corresponding bone fasteners. In an embodiment (not illustrated), therod portions 70 may be inserted into a rod-receiving member (e.g., aside-loading head, top-loading head, eye-hole loading head, etc.) of apolyaxial screw. After insertion, a locking element (e.g., a clampingscrew) may be placed onto the head to secure the rod portions 70 in therod receiving member of the respective bone fastener. One end of the rodportions 70 may comprise a cap 90, such as a flanged end. The other endof the rod portions 70 may comprise an end plate 100. As illustrated,the end of each leg 80 may extend to the corresponding end plate 100. Inan embodiment, the end of each leg 80 may be fixed to a face 110 of theend plate 100.

In accordance with embodiments of the present invention, the dynamicstabilizer 30 should allow for relative movement between bone fasteners(not illustrated) coupled to the rod portions 70. By way of example, ifa force is applied in a direction of the longitudinal axis 120 of thedynamic stabilizer 30 to move the rod portions 70 towards one another,the spring 60 should be deformed. When the force is removed, the spring60 should return to its original position. In addition, the rod portions70 can also rotate with respect to each other if a rotational force isapplied about longitudinal axis 120. Moreover, the rod portions 70 canalso be axially displaced if a force is applied in a directionperpendicular to the longitudinal axis 120.

The components of the dynamic stabilizer 30 may be made from a varietyof biocompatible materials, including metals, ceramic materials, andpolymers. Examples of biocompatible materials include titanium,stainless steel, aluminum, cobalt-chromium, alloys,polyetheretherketones (“PEEK”), and polyethylene. In an embodiment, thespring 60 may be made from titanium or a titanium alloy.

FIG. 3 illustrates dynamic stabilizer 30 in accordance with anotherembodiment of the present invention. The illustrated dynamic stabilizer30 is similar to the embodiment of FIG. 2, in that the dynamicstabilizer 30 comprises a spring 60 disposed between rod portions 70.However, unlike the spring 60 of FIG. 2 in the general shape of a V,FIG. 3 illustrates a spring 60 that is semi-elliptical in shape. Thespring 60 may be rectangular in cross section, for example. In anembodiment, the spring 60 is a semi-elliptical leaf spring. Asillustrated, the spring 60 may have a semi-elliptical portion 130 androd-connecting portions 140 that extend from either end of thesemi-elliptical portion 130. In an embodiment, the rod-connectionportions 140 may be generally parallel plates that extend from eitherend of the semi-elliptical portion 130. The rod portions 70 may beconfigured and adapted for insertion into rod-receiving members ofcorresponding bone fasteners. One end of the rod portions 70 maycomprise a cap 90, such as a flanged end. The other ends of the prodportions 70 may be coupled to the rod-connecting portions 140 of thespring 60.

FIGS. 4-6 illustrate dynamic stabilizer 30 that is laterally offset inaccordance with one embodiment of the present invention. As illustrated,dynamic stabilizer 30 comprises lateral rods 150 coupled by cross member160. Each of the lateral rods 150 may be secured to a correspondingpedicle screw 170. The lateral rods 150 may extend in a generallyparallel direction from the pedicle screws 170. As illustrated, thelateral rods 150 may be coupled by cross member 160 that extendsgenerally transverse to the lateral rods 150. In the illustratedembodiment, the cross member 160 comprises a translatable end 180 and arod-locking end 190. The translatable end 180 may be configured andadapted to slidably engage one of the lateral rods 150. In other words,the translatable end 180 may couple the cross member 160 to the lateralrod 150 while still allowing for relative movement between the crossmember 160 and the lateral rod 150. As illustrated, the translatable end180 may have an opening 200 through which one of the lateral rods 150may be disposed. In an embodiment, the translatable end 180 has a yoke210 that may be disposed over one of the lateral rods 150. Asillustrated, the yoke 210 may define the opening 200. To secure thetranslatable end 180 on the lateral rod 150, a first clamp 220 may beplaced on one end of the lateral rod 150. In an embodiment, first screw230 may be tightened to lock the first clamp 220 onto the lateral rod150. As illustrated, the translatable end 180 may be disposed over thelateral rod 150 between the pedicle screw 170 and the first clamp 220.In an embodiment, the translatable end 180 may freely move between thepedicle screw 170 and the first clamp 220.

The rod-locking end 190 may be fixedly coupled to the other one of thelateral rods 150. As illustrated, the rod-locking end 190 may beconfigured and adapted with a seat that receives the corresponding rod150. The rod-locking end 190 may be locked or otherwise tightened tosecure the lateral rod 150 in the seat. In the illustrated embodiment,the rod-locking end 190 is configured in the shape of a clamp, e.g.,second clamp 240. The second clamp 240 may define the seat that receivesthe lateral rod 150. Second screw 250 may be tightened, for example, tolock opposing surfaces 260 of the second clamp 240 down onto the lateralrod 150.

A tapered segment 270 may connect the translatable end 180 and therod-locking end 190. As illustrated, the tapered segment 270 may have agradual reduction in thickness from either end to its middle. In anembodiment, the tapered segment 270 may be generally rectangular incross section. In another embodiment (not illustrated), tapered segment270 may be generally elliptical or circular in cross section.

As illustrated by FIG. 4, the lateral rods 150 may be secured to acorresponding pedicle screw 170. The pedicle screw 170 may comprise athreaded shaft 280 for fixation into a bone and a head 290. The head 290generally may comprise a recess 300 for receiving a rod, e.g., lateralrods 150. In an embodiment, the recess 300 extends away from thethreaded shaft 280. In an embodiment, the head 290 is top loading. In analternative embodiment (not illustrated), the recess 300 may extendperpendicular to the threaded shaft 280 such that the head 290 may beside loading. One of the lateral rods 150 can be placed into the recess300. A locking element 310 (e.g. , a nut) can be threaded into the topof the head 290 to secure one of the lateral rods 150 in a correspondingrecess 300.

In accordance with embodiments of the present invention, the dynamicstabilizer 30 illustrated by FIGS. 4-6 should allow for relativemovement between the pedicle screws 70. By way of example, if a force isapplied in a direction of the longitudinal axis 120 of the dynamicstabilizer 30, the opening 200 in the yoke 210 may be sized to allowmovement of the dynamic stabilizer 30 along its longitudinal axis 120.In addition, the translatable end 180 can also slide along the lateralrod 150, for example, if a force is applied in a direction perpendicularto longitudinal axis 120. Moreover, the translatable end 180 should alsobe configured to rotate with respect to the lateral rod 150 over whichit is disposed.

FIGS. 7-9 illustrate dynamic stabilizer 30 that is laterally offset inaccordance with one embodiment of the present invention. The illustrateddynamic stabilizer 30 is similar to the embodiment of FIGS. 4-6, in thatthe dynamic stabilizer 30 is laterally offset. For example, the dynamicstabilizer comprises lateral rods 150 coupled by cross member 160. Eachof the lateral rods 150 may be secured to a corresponding pedicle screw170. In the illustrated embodiment, the cross member 160 comprises atranslatable end 180 and a rod-locking end 190. As illustrated, thetranslatable end 180 may be disposed over one of the lateral rods 150.However, unlike the first clamp 220 of FIGS. 4, the lateral rod 150comprises a flanged end 320 for securing the translatable end 10 ontothe lateral rod 150. It should be understood that other suitablemechanisms may be also used to secure the translatable end 180 onto thelateral rod 150 while allowing for the desired movement.

FIG. 10 illustrates dynamic stabilizer 30 that is laterally offset inaccordance with another embodiment of the present invention. In theillustrated embodiment, the dynamic stabilizer 30 comprises first bentrod portion 330. In an embodiment, the first bent rod portion 330 may bemade from a material that comprises PEEK. As illustrated, the first bentrod portion 330 generally may comprise first rod segment 340 and secondrod segment 350 extending from one end of first rod segment 340. In anembodiment, the second rod segment 350 extends transverse from one endof the first rod segment 340. The other end of the first rod segment 340may have a cap 360. In an embodiment, the cap 360 is a flanged end. Thefirst rod segment 340 may generally be configured and adapted forinsertion into a rod-receiving member of a bone fastener. The first bentrod portion 330 further may comprise rod connecting end 370. In anembodiment, the rod connecting end 370 may have a generally ring-shapedopening for receiving a rod.

As illustrated, the dynamic stabilizer 30 further may comprise secondbent rod portion 380. In an embodiment, the second bent rod portion 380may be made from a material that comprises PEEK. The second bent rodportion 380 generally may comprises first rod segment 390 and second rodsegment 400 extending from one end of first rod segment 390. In anembodiment, the second rod segment 400 extends transverse from one endof the first rod segment 390. The other end of the first rod segment 390may have a cap 410. In an embodiment, the cap 410 is a flanged end. Thefirst rod segment 390 may generally be configured and adapted forinsertion into a rod-receiving member of a bone fastener. The secondbent rod portion 380 further may comprise rod connecting end 420. In anembodiment, the rod connecting end 420 may have a generally ring-shapedopening for receiving a rod. As illustrated, the first bent rod portion330 and the second bent rod portion 340 may be aligned with mirror-likesymmetry such that the second rod segments 350, 400 are generallyparallel.

In the illustrated embodiment, the dynamic stabilizer 30 further maycomprise cross member 430. In an embodiment, the cross member 430 may bemade from a material that comprises PEEK. The cross member 430 may berod-like in shape. As illustrated, the cross member 430 may extendbetween the rod connecting ends 370, 420 with the rod connecting ends370, 420 disposed over the cross member 430. As illustrated, the rodconnecting ends 370, 420 may be generally ring shaped and extend aroundthe cross member 430. In an embodiment, each of the rod connecting ends370, 420 is slidable along the cross member 430 and rotatable about thecross member 430. As illustrated, a spacer 450 may be disposed over thecross member 430 between the rod connecting ends. In an embodiment, thespacer 450 may be a cylindrically shaped sleeve. In an embodiment, thespacer 450 may made from a flexible material, such as polyethyleneterephthalate. Caps 440 may be disposed on either end of the crossmember 430. In an embodiment, the caps 440 may be flanged ends.

FIG. 11 illustrates dynamic stabilizer 30 that is laterally offset inaccordance with another embodiment of the present invention. Theillustrated dynamic stabilizer 30 is similar to the embodiment of FIG.10, in that the dynamic stabilizer 30 is laterally offset. For example,the dynamic stabilizer 30 comprises first and second bent rod portions330, 380. As illustrated, the first and second bent rod portions 330,380 may each comprise first rod segments 340, 390 for insertion into rodreceiving member of a bone fastener, such as slots in head 445 of a bonefastener. In an embodiment, cross member 430 may be disposed between therod connecting ends 370, 420 of the first and second bent rod portions330, 380. However, rather than having the spacer 450 of FIG. 10 disposedbetween the rod connecting ends 370, 420, the embodiment of FIG. 11comprises two ring-shaped members 460 disposed over the cross member430. As illustrated, the each of the rod connecting ends 370, 420 maysurround a corresponding ring-shaped member 460. In an embodiment, thering-shaped members 460 may be made from a material that comprisestitanium, carbon fiber and/or PEEK.

FIG. 12 illustrates dynamic stabilizer 30 in accordance with one or moreembodiments of the present invention. As illustrated, a cross member,such as rod 470 may be disposed between pedicle screws 480. To stabilizethe rod 470 while allowing for relative movement between the pediclescrews 480, the dynamic stabilizer 30 may comprise spring washers 490disposed on either side of a translatable locking cap 500. Thetranslatable locking cap 500 should be able to secure the rod 470 to oneof the pedicle screws 480 while allowing for some movement with respectto the threaded portion of the corresponding pedicle screw 480. Clamps490 may be placed on cross member 430 to secure the spring washers 470against the translatable locking cap 480. As illustrated, one of thespring washers 470 is disposed between each of the clamps 490 and thetranslatable locking cap 480.

FIGS. 13-14 illustrate dynamic stabilizer 30 in accordance withadditional embodiments of the present invention. As illustrated, thedynamic stabilizer 30 may comprise a cross member (e.g., bowed segment520) extending between first rod connecting end 530 and second rodconnecting end 540. In an embodiment, the cross member may be made froma material comprising titanium or a titanium alloy. In the embodimentillustrated by FIG. 13, the bowed segment 520 may have a curvature thatis inwardly concave. In an alternative embodiment illustrated by FIG.14, the bowed segment 520 may be outwardly convex. When stress isapplied to one or both of first rod connecting end 530 and the secondrod connecting end 540, the bowed segment 520 should at least partiallyflex. In this manner, the dynamic stabilizer 30 should allow forrelative movement between bone fasteners to which it is attached.

In the illustrated embodiment, first rod connecting end 530 may definean opening 545 formed by rod portion 550 and arch portion 560. Asillustrated, the arch portion 560 may span from a first end 570 of therod portion 550 to a second end 580 of the rod portion 550. In anembodiment, the bowed segment 520 generally may extend from the archportion 560. The rod portion 550 may be configured and adapted forinsertion into rod receiving members of corresponding bone fasteners. Asillustrated by FIG. 14, bone fastener 590 may comprise head 610 withthreaded portion 600 extending from one end of head 610. Head 610 maycomprise slot 620 for receiving rod portion 550. After insertion of rodportion 550 into the slot 620, a locking element (e.g., a nut) may beplaced onto the head 610 to secure the rod portion 550 in the slot 620.

FIG. 15 illustrate dynamic stabilizer 30 that incorporates one or morecompressible elements 630, 640 in accordance with another embodiment ofthe present invention. As illustrated, dynamic stabilizer 30 includescross member 650 for connecting a pair of bone fasteners 660, 670. Inaccordance with the present embodiments, the cross member 630 connectsthe bone fasteners 660 with the compressible elements 630, 640 providingfor dynamic stabilization. More particularly, compression of thecompressible elements 630, 640 when one or both of the bone fasteners660, 670 moves should allow for at least some relative movement betweenthe bone fasteners 660, 670. In an embodiment, the compressible elements630, 640 may be generally ring-shaped sleeves that fit around the bonefasteners 660, 670.

FIG. 16 illustrates one of the bone fasteners 660, 670 in more detail inaccordance with an embodiment of the present invention. As illustrated,the bone fastener 670 may be a posted screw that comprises a threadedstem 680 for implantation into a bone, intermediate cylindrical portion690, flange 700 for supporting one of the compressible elements 630, 640on the cylindrical portion 690, and head 710. In an embodiment, theintermediate cylindrical portion 690 is not threaded. In an embodiment(not illustrated), intermediate cylindrical portion 690 may be threaded.One of the compressible elements 630, 640 (illustrated by FIG. 15) maybe disposed around the cylindrical portion 690 supported by the flange700. In an embodiment, the head 710 may be a threaded, cylindrical head.

FIG. 17 illustrates the cross member 650 in more detail in accordancewith an embodiment of the present invention. In an embodiment, the crossmember 650 is made from a material that comprises titanium or a titaniumalloy. As illustrated, the cross member 650 includes a tapered portion720 that extends between first connecting end 730 and second connectingend 740. Each of the first connecting end 730 and the second connectingend 740 may comprise an opening 750, 760. As illustrated, the first andsecond connecting ends 730, 740 may be generally ring shaped. In anembodiment, the openings 750, 760 may be sized to fit over thecorresponding one of the bone fasteners 640, 650. As illustrated by FIG.15, each of the first connecting end 730 and the second connecting end740 are disposed around a corresponding compressible element 630, 640.To secure the cross member 650 on the bone fasteners 660, 670, a lockingelement (e.g., nuts 770, 780) may be tightened onto the head 710 of eachof the bone fasteners 660, 670.

FIG. 18 illustrates dynamic stabilizer 30 in accordance with anotherembodiment of the present invention. The illustrated dynamic stabilizer30 is similar to the embodiment of FIG. 15, in that the dynamicstabilizer 30 incorporates one or more compressible elements 630, 640.However, unlike the cross member 630 of FIG. 15, the dynamic stabilizer30 of FIG. 18 comprises an adjustable cross member 790 that has anadjustable length. As illustrated, the dynamic stabilizer 30 comprisesan adjustable cross member 790 that extends between a first connectingend 730 and a second connecting end 740. The first connecting end 730and the second connecting end 740 may be coupled to adjacent vertebrae(not illustrated) by bone fasteners 660, 670. Compressible elements 630,640 should allow for at least some respective movement between the bonefasteners 660, 670. Dynamic stabilizer 30 further may comprise rod 800that extends from second connecting end 740. In an embodiment, the rod800 is circular in cross section. In another embodiment (notillustrated), the rod 800 is rectangular or square in cross section. Asillustrated, the rod 800 may be integrally formed with the secondconnecting end 740. In an embodiment (not illustrated), the rod 800 is aseparate piece coupled to the second connecting end 740. In theillustrated embodiment, the dynamic stabilizer 30 further comprises arod connecting portion 810 that extends from the first connecting end730. As illustrated, the rod connecting portion 810 may be integrallyformed with the first connecting end 730. In an embodiment (notillustrated), rod connecting portion 810 is a separate piece coupled tothe first connecting end 730. The rod connecting portion 810 may have anopening 820 that extends through a portion of the rod connecting portion810. The opening 820 should receive the rod 800 extending from thesecond connecting end 740. Accordingly, the adjustable cross member 790may comprise the rod connecting portion 810 having the rod 800 disposedin the opening 820 of the rod connecting portion 810. To adjust thelength of the adjustable cross member 790, the depth that the rod 800 isinserted into the opening 820 may be varied. The rod connecting portion810 may comprise one or more openings 830, 840 for receiving set screwsto secure the rod 800 in the opening 820, preventing movement of the rod800 with respect to the rod connecting portion 810.

FIG. 19 illustrates dynamic stabilizer 30 in accordance with anotherembodiment of the present invention. The illustrated dynamic stabilizer30 is similar to the embodiment of FIG. 18, in that the dynamicstabilizer 30 incorporates one or more compressible elements 630, 640,850. However, unlike the dynamic stabilizer 30 of FIG. 17 which candynamically stabilize one level of the patient's spine, the dynamicstabilizer 30 of FIG. 19 is configured and adapted to stabilizer morethan one level of a patient's spine. To span more than one level in apatient's spine, the dynamic stabilizer 30 comprises adjustable crossmember 790 for spanning a first level of a patient's spine, and secondadjustable cross member 860 for spanning a second level of the patient'sspine. As illustrated, the adjustable cross member 790 extends betweenthe first connecting end 730 and the second connecting end 740. Thefirst connecting end 730 and the second connecting end 740 may becoupled to adjacent vertebrae (not illustrated) by bone fasteners 660,670. Compressible elements 630, 640 should allow for at least somerespective movement between the bone fasteners 660, 670. The firstconnecting end 730 may include a rod connecting end 810 having anopening 800 for receiving a rod 800. As illustrated, the rod 800 mayextend from the second connecting end 740. To adjust the length of theadjustable cross member 790, the depth that the rod 800 is inserted intothe opening 820 may be varied. In this manner, the adjustable crossmember 790 may span across a first level of a patient's spine.

As illustrated by FIG. 19, the second adjustable cross member 860extends between the second connecting end 740 and the third connectingend 870. In the illustrated embodiment, the third connecting end 870 isdisposed around compressible element 850, which is disposed on the bonefastener 880. Compressible element 850 may be disposed around anintermediate portion of bone fastener 880. A locking element (e.g., nut890) may be placed onto the bone fastener 880 to secure the thirdconnecting end 870 on the bone fastener 880. In an embodiment,compressible element 850 may be a generally ring-shaped sleeve that fitsaround the bone fastener 880. As illustrated, second rod 900 may extendfrom the second connecting end 740 in the opposite direction of rod 800.In addition, second rod connecting portion 910 may extend from the thirdconnecting end 870. The second rod connecting portion 910 may have anopening (not illustrated) that extends through a portion of the secondrod connecting portion 910. The opening should receive the second rod900 extending from the second connecting end 740. Accordingly, thesecond adjustable cross member 860 may comprise the second rodconnecting portion 910 having the second rod 900 disposed in the openingof the second rod connecting portion 910. To adjust the length of thesecond adjustable cross member 860, the depth that the second rod 900 isinserted into the opening may be varied. In addition, the second rodconnecting portion 910 may comprise one or more openings 920, 930 forreceiving set screws to secure the second rod 900 in the opening,preventing movement of the second rod 900 with respect to the second rodconnecting portion 910. However, the compressible elements 640, 850should allow for respective movement between the bone fasteners 670, 880interconnected by the second adjustable cross member 860.

While it is apparent that the invention disclosed herein is wellcalculated to fulfill the objects stated above, it will be appreciatedthat numerous modifications and embodiments may be devised by thoseskilled in the art.

What is claimed is:
 1. A surgical method comprising: inserting a spinestabilization into a patient, wherein the spine stabilization systemcomprises: a first bone fastener configured to attach the spinestabilization system to a first vertebra; a second bone fastenerconfigured to attach the spine stabilization system to a secondvertebra; a dynamic spine stabilizer operably connected to the firstbone fastener and the second bone fastener, wherein the dynamic spinestabilizer is capable of at least some movement between the first bonefastener and the second bone fastener.
 2. The surgical method of claim1, wherein the dynamic spine stabilizer comprises a first lateral rodand a second lateral rod coupled by a cross member.
 3. The surgicalmethod of claim 2, wherein the first lateral rod is received in thefirst bone fastener and the second lateral rod is received in the secondbone fastener.
 4. The surgical method of claim 2, wherein the firstlateral rod is top loaded into the first bone fastener and the secondlateral rod is top loaded into the second fastener.
 5. The surgicalmethod of claim 2, wherein the dynamic spine stabilizer comprises atranslatable end and a rod-locking end.
 6. The surgical method of claim5, wherein the translatable end comprises a yoke that is disposed overthe first lateral rod.
 7. The surgical method of claim 6, wherein thespine stabilization system further comprises a first clamp placed on thefirst lateral rod, wherein the yoke is disposed between the first bonefastener and the first clamp.
 8. The surgical method of claim 7, whereinthe translatable end is freely movable between the first bone fastenerand the first clamp.
 9. The surgical method of claim 5, wherein therod-locking end comprises a second clamp having a seat for receiving thesecond lateral rod, wherein the rod-locking end further comprises ascrew to lock opposing surfaces of the second clamp onto the secondlateral rod.
 10. The surgical method of claim 9, wherein the crossmember is tapered.
 11. A surgical method comprising: inserting a spinestabilization into a patient, wherein the spine stabilization systemcomprises: a first bone fastener configured to attach the spinestabilization system to a first vertebra; a second bone fastenerconfigured to attach the spine stabilization system to a secondvertebra; a dynamic spine stabilizer operably connected to the firstbone fastener and the second bone fastener, wherein the dynamic spinestabilizer comprises a first lateral rod and a second lateral rodconnected by a cross member.
 12. The surgical method of claim 11,wherein the dynamic spine stabilizer comprises a translatable end and arod-locking end.
 13. The surgical method of claim 12, wherein thetranslatable end is attachable to the first lateral rod and therod-locking end is attachable to the second lateral rod.
 14. Thesurgical method of claim 13, wherein in a final construct, thetranslatable end is moveable relative to the first lateral rod and therod-locking end is fixed relative to the second lateral rod.
 15. Thesurgical method of claim 13, wherein the spine stabilization systemfurther comprises a first clamp placed on the first lateral rod.
 16. Thesurgical method of claim 15, wherein the translatable end is positionedbetween the first clamp and the first bone fastener.
 17. The surgicalmethod of claim 11, wherein the first lateral rod is top loaded into thefirst fastener and the second lateral rod is top loaded into the secondfastener.
 18. The surgical method of claim 17, wherein the dynamic spinestabilizer further comprises a translatable end and a rod-locking end.19. The surgical method of claim 18, wherein the translatable end isattachable to the first lateral rod and the rod-locking end isattachable to the second lateral rod.
 20. The surgical method of claim19, wherein in a final construct, the translatable end is moveablerelative to the first lateral rod and the rod-locking end is fixedrelative to the second lateral rod.